1. Field of the Invention
The present invention relates to a mobile terminal device provided with a plurality of keys, each of which is assigned a plurality of characters.
2. Description of the Related Art
Heretofore, a mobile terminal device such as a mobile telephone has been provided with a plurality of keys (e.g., numeric keys “0” to “9” and symbol keys “*” and “#”) in order for a user to enter a telephone number. In such a mobile terminal device, each key is assigned characters in order for the user to enter the characters when the user creates an e-mail message, or the like. Each key is assigned a plurality of characters because the number of keys provided for the mobile terminal device is limited on account of the portability of the mobile terminal device.
Specifically, when the user presses a key, the mobile terminal device switches display from one character to another on a display region. Then, when the user performs operation for character finalization, the mobile terminal device converts a character displayed on the display region to a finalized character. Incidentally, the operations for character finalization include the user's operation of pressing a different key from the key assigned the character displayed on the display region, and the user's operation of pressing a cursor key.
For example a mobile terminal device in which the numeric key “1” is assigned hiragana characters specifically “a,” “i,” “u,” “e,” and “o,” belonging to the first, specifically “a” column of the Japanese kana syllabary. Each time the user presses the numeric key “1,” the mobile terminal device switches display from “a” to, in turn, “i,” “U,” “e,” and “o.” When the user presses the numeric key “2” or the cursor key under a condition where “u” is displayed on the display region, the mobile terminal device converts “u” displayed on the display region to a finalized character.
A method of entry mentioned above (hereinafter referred to as a “five-touch method”) involves complicated operations for character entry, because the user, even in a case where the user wants to make sequential entries of characters assigned to one key, has to press some other key in order to convert the character displayed on the display region to a finalized character.
For example, in a case where the user wants to enter the hiragana characters “i” and “e” in sequence, the user cannot convert “i” to a finalized character unless performing the operation for character finalization while “i” is displayed on the display region.
Also proposed is a mobile terminal device which has a function of detecting a user touching a key with the user's finger and converting a displayed character to a finalized character when the user moves one's finger off the key while the character is displayed on the display region (see, for example, Unexamined Japanese Patent Application No. 2002-55766, claim 1, FIG. 7, and so on). Such a mobile terminal device saves the user having to perform the operation for character finalization and thus facilitates the user's operations for character entry.
However, the mobile terminal device, which is designed to convert a displayed character to a finalized character when a user moves one's finger off a key while the character is displayed on the display region, converts an unintended character to a finalized character when the user moves one's finger off the key in situations where the user changes one's grip to hold the mobile terminal device or does the like.
Moreover, as a mobile terminal device such as a cellular phone, there has heretofore been known a mobile terminal device in which function keys for executing an on-hook function, an off-hook function, a function of calling a menu screen and the like are provided, in addition to 12 keys (“0” to “9,” “*” and “#”) for entering a telephone number and the like. Recently, mobile terminal devices feature sophisticated functions. Thus, in order for a user to utilize the sophisticated functions, a plurality of functions are assigned to the 12 keys and the function keys.
In such a mobile terminal device, the functions assigned to the keys differ according to an operation mode of the mobile terminal device. For this reason, it is difficult for the user to figure out the functions assigned to the keys. Consequently, a false key operation is likely to occur.
It is assumed that the mobile terminal device is used in dark surroundings. In this assumed case, even if the user has figured out the functions assigned to the keys, the false key operation is likely to occur when the user operates the mobile terminal device in the dark surroundings.
Meanwhile, as a mobile terminal device intended to prevent the false key operation, there has been proposed a mobile terminal device which has a function of detecting a user touching the keys. In the case of a mobile terminal device of this type, when the user touches any of the keys, an explanation on a function which is assigned to the key touched by the user is displayed before the user presses the key (see for example, Unexamined Japanese Patent Application No. 2002-55766).
Specifically, upon detection of a user's finger touching any of the keys, the mobile terminal device displays, in a display area, a character assigned to the key touched by the user. Moreover, upon detection of the user's finger moving away from the key, the mobile terminal device finalizes the character displayed in the display area.
Incidentally, as a method of detecting the user touching the keys, an analog method and a discrete method are cited.
As one of the analog methods, there is a resistive film method using a resistive film. In the resistive film method, a voltage value is obtained by resistive division to detect the user touching the keys. On the other hand, in the discrete method, a plurality of detecting elements are provided for each of the keys. In one of the discrete methods, a capacity, which is generated between an electrode provided for each key and the human body, is obtained. Thereafter, by detecting an electrode of which capacity is changed, a touch on any of the keys by the user is detected.
Generally, in the analog method, coordinates of only one point can be detected. On the other hand, in the discrete method, coordinates of two points or more can be detected. As a result, when the discrete method is applied to a touch pad, detection can be made for the user touching a plurality of keys. Thus, there is an advantage that the range of user interface design is expanded.
However, when the user tries to touch one key and accidentally touches more than one key, it is difficult to identify the key which the user has intentionally touched.
As a mobile terminal device such as a cellular phone, there has heretofore been known a mobile terminal device in which function keys for executing an on-hook function, an off-hook function, a function of calling a menu screen and the like are provided, in addition to 12 keys (“0” to “9,” “*” and “#”) for entering a telephone number and the like. Recently, mobile terminal devices feature sophisticated functions. Thus, in order for a user to utilize the sophisticated functions, a plurality of functions are assigned to the 12 keys and the function keys.
In such a mobile terminal device, the functions assigned to the keys differ according to an operation mode of the mobile terminal device. For this reason, it is difficult for the user to figure out the functions assigned to the keys. Consequently, a false key operation is likely to occur.
It is assumed that the mobile terminal device is used in dark surroundings. In this assumed case, even if the user has figured out the functions assigned to the keys, the false key operation is likely to occur when the user operates the mobile terminal device in the dark surroundings.
Meanwhile, as a mobile terminal device intended to prevent the false key operation, there has been proposed a mobile terminal device which has a function of detecting a user touching the keys. In the case of a mobile terminal device of this type, when the user touches any of the keys, an explanation on a function which is assigned to the key touched by the user is displayed before the user presses the key (see, for example, Unexamined Japanese Patent Application No. 2002-55766).
Specifically, upon detection of a user's finger touching any of the keys, the mobile terminal device displays, in a display area, a character assigned to the key touched by the user. Moreover, upon detection of the user's finger moving away from the key, the mobile terminal device finalizes the character displayed in the display area.
Incidentally, as a method of detecting the user touching the keys, an analog method and a discrete method are cited.
As one of the analog methods, there is a resistive film method using a resistive film. In the resistive film method, a voltage value is obtained by resistive division to detect the user touching the keys. On the other hand, in the discrete method, a plurality of detecting elements are provided for each of the keys. In one of the discrete methods, a capacity, which is generated between an electrode provided for each key and the human body, is obtained. Thereafter, by detecting an electrode of which capacity is changed, a touch on any of the keys by the user is detected.
Generally, in the analog method, coordinates of only one point can be detected. On the other hand, in the discrete method, coordinates of two points or more can be detected. As a result, when the discrete method is applied to a touch pad, detection can be made for the user touching a plurality of keys. Thus, there is an advantage that the range of user interface design is expanded.
However, when the user tries to touch one key and accidentally touches more than one key, it is difficult to identify the key which the user has intentionally touched.